Chrome plating solutions are formed by chrome oxides dissolved in water to form chromic acid. These solutions are maintained at temperatures substantially above normal room temperature (e.g. 135.degree. F.) and are continuously agitated during the plating process. As a consequence a substantial amount of liquid and vapor escapes from the tank. A dense mist forms in the atmosphere just above the plating solution surface. The mist contains a considerable amount of hexavalent chrome which must be segregated from the ambient atmosphere.
In the past the chrome bearing mist was swept from the plating solution surface by exhaust systems. The typical exhaust system was formed by a hood located adjacent the plating solution surface, a duct system leading from the building and an induction fan for drawing the mist into the hood and duct and exhausting the mist to atmosphere.
The amount of chrome introduced into the environment by such exhaust systems was excessive and considered a health hazard. Accordingly proposals were made for removing chrome from the mist. In some proposals the exhaust fans directed the mist through filters which removed chrome before it could be exhausted to atmosphere. In other proposals the mist was directed through scrubbers which removed the chrome. The chrome removed by these devices was sometimes collected and disposed of as a toxic waste material or was processed further to reclaim it for eventual reuse.
Chrome compounds are expensive materials. Reclamation was thus an attractive alternative to disposal as toxic waste or even exhausting chrome bearing mist to atmosphere. Reclamation required capital expenditures and incurred operating costs which reduced its attractiveness. Furthermore the prior art schemes failed to eliminate a small, but environmentally significant, percentage of the total chrome in the plating tank mist. This chrome was exhausted into the atmosphere.
The present invention provides a new and improved method and apparatus for removing chrome from plating solution mists wherein virtually all the chrome is removed from the effluent chrome plating solution mist before it is exhausted to atmosphere, the chrome is reclaimed for immediate reuse in the plating solution and the capital and operating expenses required for reclamation are not significant.